Hydraulic press



Oct. 6, 1970 PAPPAS 3,531,966

HYDRAULIC PRESS Filed April 25, 1968 2 Sheets-Sheet 1 Uted States Patent O 3,531,966 HYDRAULIC PRESS Lambros Pappas, Chicago, Ill., assignor to Verson Allsteel Press Company, Chicago, Ill., a corporation of Dela- Ware Filed Apr. 2s, 196s, ser. No. 724,107

Inf. cl. nzid 2.2/12 U.s. Cl. 72-63 3 Claims ABSTRACT OF THE DISCLOSURE There is disclosed a hydraulic press of the type utilizing an expandable pressure cell or diaphragm for shaping a workpiece around a form disposed within a cavity. The cavity is defined by means including coaxial inner and outer cylinders having a narrow space therebetween filled with hydraulic fluid which is pressurized during operation of a press for promoting more uniform distribution of stresses or reaction forces around the cylinders.

The present invention relates to a novel press, and more specifically to a novel hydraulic press.

It has heretofore been suggested to provide structures of the general type contemplated herein with cylindrical body means defining a cavity and a hydraulically expandable fluid cell or diaphragm disposed Within the cavity for engaging a workpiece disposed on a mold or form supported on a tray member and causing the workpiece to assume the shape of the form. During the operation of such a structure, reaction forces which occur as the fluid cell or diaphragm is expanded and fills the cavity are absorbed and sustained by the outer cylinder or body means.

While presses of the above described general type have been operated successfully, the structures have been such that reaction forces are transmitted to the cylinder or body means unevenly. In certain instances, the uneven loading of the cylinder has resulted in sufficiently high concentrations of stresses in limited areas to cause failure.

An important object of the present invention is to provide a novel hydraulic press structure of the above described type which is constructed for promoting more uniform distribution of reaction forces around the outer cylinder or body means and thereby minimizing any possibility of high stress concentrations and failure.

A more specific object of the present invention is to provide a novel hydraulic press of the above described type `wherein the outer cylindrical body means comprises a relatively heavy and rigid outer cylinder and means for transmitting reaction forces from the interior of the press hydraulically more uniformly around the interior of the cylinder. Still more specifically it is contemplated that the cylindrical body means of the press shall include an inner cylinder concentrically disposed with repsect to the outer cylinder with an annular space therebetween filled with hydraulic liquid for aiding in transmitting the reaction forces more uniformly to the outer cylinder.

Other objects and advantages of the present invention will become apparent from the following description and the accompanying drawings wherein:

FIG. 1 is a simplified perspective view showing a press incorporating features of the present invention;

FIG. 2 is an end view of the press shown in FIG. 1;

FIG. 3 is an enlarged fragmnetary sectional view taken along line 3-3 in FIG. 1; and

FIG. 4 is a fragmentary sectional view taken along line 4-4 in FIG. 3.

Referring now more specifically to the drawings wherein like parts are designated by the same numerals throughout the various figures, a press incorporating features of the present invention is shown in FIGS. 1 and 2. The press comprises cylinder or body means 12 mounted on a suitable frame 14. Table extensions 16 and 18 are located at opposite ends of the cylinder. A work supporting tray 20 (see FIGS. 3 and 4) is adapted to be shifted from within the body means to retracted positions on the table extensions 16 and 18 for loading and unloading.

A suitable source of hydraulic fluid under pressure is provided for actuating the press. In the embodiment disclosed herein, this comprises a pump and motor unit 22 having an inlet connected with a reservoir 24 as shown schematically in FIGS. 2 and 4. An outlet of the pump is connected with a control valve 26 which in turn has an outlet connected with a fluid supply line 28. The control valve also has a vent port connected with a return line 30 which extends back to the reservoir 24.

As shown in FIGS. 3 and 4, the cylindrical body means 12 comprises an outer thick walled relatively rigid and strong cylinder member 32 and an inner cylinder 34. The wall of the inner cylinder member 34 is relatively thin and resiliently yieldable as compared with the outer cylinder member for a purpose to be described below. It is to be noted that the cylinders are concentrically disposed and the outside diameter of the cylinder 34 is slightly less than the inside diameter of the cylinder 32 so that a narrow annular space 36 is defined between the cylinders.

Opposite end portions 38, only one of which is shown, of the inner cylinder 34- are enlarged for snugly fitting within the outer cylinder and 4closing opposite ends of the annular Space 36. In addition, sealing rings 40 and 42 are provided between the outer cylinder and the enlarged end portions 38 of the inner cylinder so that the annular space 36 is effectively sealed and is adapted to receive and retain hydraulic fluid under pressure as will be described.

As shown in FIG. 4, fluid passageways 44 and 46 are formed in the inner cylinder. These passageways connect with the annular space 36 and also with branch conduits 48 and 50 which in turn connect with the fluid supply line 28.

The cylindrical body means surrounds a cavity 52 into which the aforementioned tray 20 is adapted to be inserted. A relatively thick and rigid floor casting 54 having an outer curved surface mating with the interior surface of the inner cylinder 34 fits within a lower portion of the cylinder and defines a floor for the cavity 52. Bearing strips or rails 56 and 58 are mounted longitudinally of the floor casting S4 which extends for the entire length of the cylindrical members. Spring biased rollers, not shown, of a known construction are mounted at opposite ends of the tray and ride on the rails 5'6 and 58 for facilitating movement of the tray 20 into and out of the cavity. These rollers normally raise the trays slightly above the bottom of the cavity, but collapse under the pressure applied to the tray during operation of the press so that the trays rest firmly against the bottom of the cavity in the manner shown.

A roof casting 60 similar to the floor casting 54 is disposed in and fixed against an upper portion of the inner cylinder 34 and a thick relatively rigid roof plate 62 is disposed beneath and in abutting relationship to the roof casting 60. Disposed beneath and connected to the roof plate 62 is an expandable fluid cell or bag 66 having its lower face lined by a relatively thick tough rubber diaphragm 68. The fluid cell is provided with an inlet port 70 which communicates with a fluid passageway 72 extending longitudinally of the roof plate 62 and connected by a branch conduit 74 with the fluid supply line 28 as shown in FIG. 4.

As will be understood, the fluid cell comprising the bag 66 and diaphragm 68 will be extended into the cavity 52 on the introduction of hydraulic fluid under pressure. The action is such that the diaphragm engages the work and causes it to be pressed against and formed around the mold or form on -which it is supported in the tray 20.

The tray has a bottom section 76 and opposite diverging and upwardly extending side wall sections 78 and 80 as shown in FIG. 3. In addition, the tray has opposite end wall sections 82, only one of which is shown in FIG. 4, so that the side and end walls define a recess 84 into which work to be processed or formed is placed.

Opposite side rail members 86 and 88 extend longitudinally the length of the cylinders between the opposite side walls of the tray and the inner cylinder 34 as shown in FIG. 3. These side rails extend `between the floor casting 54 and the diaphragm "68 and serve to support the diaphragm as well as to retain and guide the tray. The rails have outer surfaces which are curved so as to mate with the inner surface of the cylinder 34. In addition, the rails have lower inclined inner surface portions 90 and 92 parallel to the inclined outer surfaces of the tray opposite side walls 78 and 80. Tray backup rails 91 and 93 extend for the full length of and are mounted on the side walls 78 and 80 for direct engagement with the surfaces 90 and 92 during operation of the press as described below. As shown in the drawings, the upper margin of the tray terminates well below the diaphragm when the diaphragm is in a retracted condition and portions of the side rails 86 and 88 extending above the tray have substantially perpendicular inner surface sections 94 and 98.

In order to seal the space between the upper margin of the tray and the diaphragm, a sealing ring member 100 is provided. This member has opposite side elements 102 and 104 with outer surfaces mating with the previously mentioned surfaces 94 and 98. Inner surfaces 106 and 107 of these side elements are beveled or inclined downwardly and inwardly as are the inner surfaces of the opposite side and end walls of the tray. The sealing ring has opposite end portions 108, only one of which is shown in FIG. 4, also having downwardly and inwardly beveled inner surfaces 110. These end portions cooperate with thickened opposite end sections 112, only one of which is shown, of the roof plate 62 as shown in PIG. 4 for substantially closing the opposite ends of the work cavity. In addition, a sealing strip or molding 114 is disposed between each end of the diaphragm 68 and each of the thickened end sections 112 of the roof plate, for retaining the diaphragm and cooperating with an adjacent end portion 108 of the sealing ring 100 in effectively sealing the opposite ends of the work cavity.

During operation of the press, the reaction forces due to the hydrostatic forces within the fluid cell are transmitted primarily through the relatively thick and rigid roof and floor structures and the side rails 86 and 88 to the inside surface of the cylinder 34. The tray absorbs the hydrostatic forces applied to its inside surface and restricts the forces from being transmitted outwardly to the cylinder. The hydrostatic pressure within the fluid cell is unevenly transmitted to the inside surface of cylinder 34 due to the interaction of the internal structural components. This induces non-uniform stress distribution on the inside surface of cylinder 34 and tends to cause areas of high stress concentration.

In accordance with the present invention, the adverse effect of such uneven stress distribution is overcome by the dual coaxial cylinder structure. The relatively thin inner cylinder 34 has a low flexural rigidity, allowing the Contact stress at its inner surface to be nearly uniform regardless of the different flexural rigidity of the mating parts.

This space 36 between the cylinders is as previously indicated connected with the fluid supply line 28. When the control valve 26 is operated to admit fluid under pressure to supply line 28 and thus expand and extend the diaphragm 68 for processing a workpiece, the pressure of the fluid in the annular chamber 36 is increased so as to substantially equal the pressure of the lluid within the diaphragm or fluid cell. Thus, the outer cylinder 32 is subjected to a uniform hydrostatic pressure simultaneously with the fluid cell. Hydrostatic pressure in the chamber 3-6 is applied over the full length of the internal pressurized zone provided by the fluid cell, and the pressure in chamber 36 equalizes thel internal pressure on cylinder 34. Thus, the internal and external forces on cylinder 34 balance each other and the inner cylinder is in a state of near equilibrium.

While a preferred embodiment of the present invention has been shown and described herein, it is obvious that many structural details may be changed without departing from the spirit and scope of the appended claims.

The invention is claimed as follows:

1. In a hydraulic press, the combination comprising body means defining a cavity and including inner and outer concentric continuous cylinders, a tray member removably disposed in said cavity for supporting work to be processed, resiliently expandable fluid pressure cell means mounted in said cavity opposite from said tray member for processing the work, a floor member supporting said tray member and having an outer arcuate surface mating with said inner cylinder, a roof structure supporting said cell means and having an outer surface mating with said inner cylinder, opposite side rail members between said floor member and said cell means and extending along opposite sides of said tray member and having outer arcuate surfaces mating with said inner cylinder, said body means including a substantially unobstructed cylindrical fluid pressure chamber means between said inner and outer cylinders, and continuously open fluid passageway means interconnecting said fluid cell means and said chamber means and being connectable with a common source of fluid under pressure for promoting the uniform distribution of reaction forces throughout and minimizing stress concentrations in said outer cylinder.

2. A combination, as defined in claim 1, wherein said outer cylinder has a relatively thick and rigid wall and said inner cylinder has a relatively thin wall.

3. A combination, as defined in claim 2, which includes elongated members secured to opposite sides of said tray member for engaging said side rails and imparting radial loads thereto.

References Cited UNITED STATES PATENTS 667,525 2/1901 Huber 72-60 2,848,968 8/1958 Novak 72--63 2,962,994 12/1960 Wheelon 72-63 3,379,043 4/1968 Fuchs 72-56 RICHARD I. HERBST, Primary Examiner 

